The length of hoses and electrical cables between a truck tractor and an associated trailer connected thereto must be such as to allow the tractor to be positioned at a sharp angle to the trailer, as when parking a trailer. The length is thereby such that if not supported, the hoses and cables would sag low enough in normal highway operation to be damaged by or to cause damage to underlying mechanical components. For this reason, it is desirable that intermediate portions of the hoses and cables be supported.
It is also desirable that swinging movements of the hose or cables or minimized. This is especially true for oscillatory movements which might build up to a large amplitude in response to rhythmic forces developed during operation at certain speeds or over certain highways. Such movements and the attendant continual flexing and rubbing of the lines, cables and support mechanism can lead to excess wear and fatigue failure.
In the prior art, there are various support devices which have heretofore been disclosed. One type is a cab-mounted support, such as illustrated in Dobrikin U.S. Pat. No. 2,948,450. It comprises a bracket assembly mounted on the rear upper surface of the cab having a spring-loaded slidable and swivelable arm extending over the space between the tractor and trailer. The flexible hose elements may be supported from the arm by spring means. While quite functionable, this type must be secured to the thin metal shell of the cab, an undesirable feature for certain purposes. It may also suffer from proneness to the aforementioned oscillation problem, particularly when the hoses and cables are suspended from the support arm by springs.
Another type, which has received considerable acceptance, is the support post type. In this type the hoses and cables are suspended from the upper portion or intermediate portion of an upstanding post on the tractor frame.
In one embodiment of the support post type the lower end of a vertical post member is secured to the upper end of an upstanding coiled spring. The lower end of the spring is secured to a supporting structure. This construction is relatively inexpensive. It suffers, however, from a tendency to built-up oscillatory movements under certain circumstances and related fatigue-failure problems.
Another embodiment of the support post type is illustrated, for example, in Dobriken U.S. Pat. No. 2,984,445. In this type, a coiled compression spring is mounted within a cylindrical housing which rests on a base plate. A first retainer is secured within the housing and engages the lower end of the spring while a second retainer engaging the upper end of the spring is coupled to a tension member to the base plate. The housing is held by the spring in an upright position but is pivotal about a fulcrum point at the lower edge of the housing, against the force of the spring. An elongated vertical member projects upwardly from the upper end of the housing and carries a cable support structure at its upper end. The vertical member is typically in the form of a rod or tube having an outside diameter much less than that of a housing member. There is a diameter reduction section between the upper end of the spring housing member and the lower end of the vertical post member.
Still another embodiment of the support post type is similar to that already described but has a fixed spring housing, the upper end of which provides a base for the pivotal action. The member resting thereon is connected through a diameter reduction section to the lower end of the post member and is coupled to the spring within the spring housing.
The latter two embodiments of the support post type have been quite satisfactory in use. They have an advantage in that, with proper design, the transverse force required to initiate tilting movement is of substantial magnitude and greater than the forces encountered except when parking maneuvers or the like. As a result, the possibility of oscillatory action is minimized. Unfortunately, these embodiments are relatively expensive. They also are subject to failure from fatigue.